The present invention relates to an electrochemical cell that includes a stacked or rolled arrangement of electrode plates, and a current collector device disposed in the cell that forms an electrical connection with the electrode plates within the cell and permits transfer of current out of the cell via an opening in the cell pouch housing.
Battery packs provide power for various technologies ranging from portable electronics to renewable power systems and environmentally friendly vehicles. For example, hybrid electric vehicles (HEV) use a battery pack and an electric motor in conjunction with a combustion engine to increase fuel efficiency. Battery packs are formed of a plurality of battery modules, where each battery module includes several electrochemical cells. The cells are arranged in two or three dimensional arrays and are electrically connected in series or in parallel. Likewise, the battery modules within a battery pack are electrically connected in series or in parallel.
Different cell types have emerged in order to deal with the space requirements of a very wide variety of installation situations, and the most common types used in automobiles are cylindrical cells, prismatic cells, and pouch cells. Regardless of cell type, each cell may include a cell housing and an electrode assembly disposed in the cell housing. The electrode assembly includes a series of stacked or rolled positive electrode plates that alternate with negative electrode plates and are separated by an intermediate separator plates. Each cell may also include a first current collector that is electrically connected to the positive electrode plates and joins the positive electrode plates to a positive cell terminal disposed outside the cell housing, and a second current collector that is electrically connected to the negative electrode plates and joins the negative electrode plates to a negative cell terminal disposed outside the cell housing.
In a pouch cell, the first and second current collectors typically each include a lead tab that passes out of the pouch between two stacked layers of pouch fabric and along a weld line that joins the layers of pouch fabric together and forms a sealed joint. The lead tab is used to pass current from inside the pouch cell housing to the outside where it can be electrically connected to an external structure such as a terminal. A special sealing tape is used to surround the lead tab at the sealed joint where the lead tab passes between the layers and out of the pouch. The sealing tape is relatively expensive since it is required to have very specific material properties. For example, the sealing tape is required to remain solid, tacky and pliable in all conditions except when localized heat is applied as occurs during the pouch fabric welding operation. When localized heat is applied, the sealing tape is required to melt, flow into open gaps between materials, and bond to both the pouch material and the respective lead tabs. A need exists for a relatively simple and less costly structure for passing current from inside the pouch cell housing to the outside where it can be electrically connected to an external structure such as a terminal or another cell.